Sunday, March 02, 2008

Ethanol - Crunching some numbers

Replacing just 10 percent of the nation's gasoline with ethanol requires an area three times the size of Texas for the process to be self-sustaining

I previously addressed some dubious efficiency claims being made by ethanol proponents
here and looked at the economics and sustainability of ethanol production here. This post takes a look at the analysis of energy use in ethanol production presented in The Futility of Ethanol essay.

1. Production of ethanol using fossil fuels. The following analysis is presented in The Futility of Ethanol.

Crunching the numbers above, converting just 10% of our gasoline to ethanol will require 14 billion gallons of ethanol, 5.014 billion NEW bushels and 34.4 million NEW acres of Corn, an increase of 48% over our 5 year historical average, requiring an area the size of North Carolina and producing 24 million tons of byproduct.

Remember that little number, the 1.52 GGE. One way to interpret the GGE that the addition of 10% ethanol will result in a 3.4% increase in total gasoline consumption ((0.52/1.52) x 10% =3.4%). Another way is to assume that we must produce 52% more ethanol than the gasoline that it replaces. Now we're talking about 21.3 billion gallons, 7.62 billion NEW bushels and 52.3 million NEW acres, an increase of 76% over our 5 year historical average, or area the size of Kansas and 36.5 million tons of DDG.

This analysis is premised on ethanol replacing 10% of the energy of gasoline to make E10. That is not correct, it replaces 10% of the gas by volume, but not energy. E10 has a Gallon Gas Equivalent (GGE) of 1.035; hence for E10, 140 billion gallons times 1.035 equals 145 billion gallons of E10 to be equivalent to the nation's gasoline use. With 10% of E10 being ethanol, 14.5 billion gallons of ethanol are needed to convert the nation to E10.

Dividing 14.5 billion by 2.8 gallons per corn bushel, results in 5.2 billion bushels of corn. With 145.8 bushels per acre, 35.5 million acres are needed to produce the corn to replace 10% of the United States gasoline used as motor fuels when powered by fossil fuels. Somewhat less than the 52 million acres in the above analysis, but still a big number.

Production of ethanol using ethanol. From my previous post.
A 1.06 energy ratio means that you need to use 16.7 gallons of ethanol to produce 17.7 gallons of the product, a net gain of one gallon of ethanol. This can be justified from an energy perspective, but it doesn’t make any sense from a business standpoint. There is too much risk and too large of an investment for that small return.

Likewise, you would have to grow 16.7 acres of corn, for a net gain of ethanol equal to the yield from only one acre.
In order to create the energy and corn to produce 1 gallon of ethanol for use as a motor fuel, 17.7 gallons of ethanol must be produced. Therefore, 16.7 times 35.5 million acres, or more than 590 million acres, of corn must be grown to convert 10% of current gasoline to ethanol.

920,000 square miles or a
n area more than three times the size of Texas! Converting that large of an area solely to ethanol production is not agriculturally sustainable. Especially for only 10% of the U.S. gasoline needs.

The E25 requirement being proposed in the Wisconsin Legislature shows the ignorance of the proponents, as it requires an area 3.5 times the size of Alaska if implemented nationwide and fueled by ethanol. That is approximately 80% of the contiguous United States.

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